1. Field of the Invention
The present invention relates to a semiconductor wafer cassette, in particular, to one comprising support slabs and broadened slots.
2 Description of Related Art
A semiconductor wafer cassette is a typical device for storing, transporting, and processing of the silicon wafers. In general, a semiconductor wafer cassette is designed so as to receive at least one silicon wafer. More specifically, the semiconductor wafer cassette mainly comprises a plurality of slots, and each slot can receive one silicon wafer.
FIG. 1 is a perspective view of a conventional semiconductor wafer cassette. The semiconductor wafer cassette 10 includes a front surface 16, a back surface 17, a left side wall 14, pairs of left dividers 18a and right dividers 18b, and a right side wall 15, wherein the four walls together define an internal bay portion for receiving a plurality of wafers parallel to each other. The semiconductor wafer cassette further includes a pair of parallel legs 22, 23 for supporting the cassette 10, and a handle 13 for facilitating handling of the cassette 10.
FIG. 2 is an elevational view of the semiconductor wafer cassette shown in FIG. 1. Each of the opposite side walls 14 and 15 is provided on the inner surface thereof with a plurality of alignment grooves 19, wherein the alignment grooves and the side walls 14 and 15 together define 25 slots with a width of 6.35 mm, and one silicon wafer can be placed in each slot.
FIG. 3 is a schematic view for illustration of a wafer warp condition within the semiconductor wafer cassette shown in FIG. 1. It is obvious that the wafer placed inside the slot droops at the central part because the whole wafer is only supported by the left dividers 18a and right dividers 18b while the central part is in a suspended state and, under the influence of gravity, the central part droops naturally; the phenomenon becomes more and more evident when the diameter of silicon wafer is greater or when the thickness of the wafer is thinner. Moreover, the wafer warps because of the central droop of the wafer, thus even if the wafer is later taken out from the cassette and put on a workbench, the wafer will be still in a U shape with two sides bending upward. The relationship between the wafer""s drooped value in the semiconductor wafer cassette and the wafer""s warped value on the workbench is shown in Table 1. The wafer""s deformation brings up difficulty in processes such as the precision of loading and unloading of the polishing machine and wafer mounter. In a serious condition, the deformation can even cause the wafer no longer usable, and thus results in the raise of the production cost, low yield, and low productivity.
Besides, the width of conventional semiconductor wafer cassette is only 6.35 mm; such a small width eventually makes the wafer inside the cassette easy to touch each other and results in mechanical damages due to warping of the wafer. This can also increase the product cost, or sometimes even cause the processing machines to break down, and thus an improvement in this regard is also needed.
An object of the present invention is to provide a semiconductor wafer cassette which is able to prevent drooping of the wafer inside the cassette.
Another object of the present invention is to provide a semiconductor wafer cassette that can improve wafer""s warp to a certain extent.
Still another object of the present invention is to provide a semiconductor wafer cassette which prevents the wafer from contacting each other during transportation so as to avoid wafer damage and processing machine""s breakdown.
To achieve the objects above, the present invention discloses a semiconductor wafer cassette, which is able to receive at least one wafer, comprising: a first side wall, a second side wall opposite to the first side wall, a front surface displaced between the first side wall and the second side wall, and a back surface displaced between the first side wall and the second side wall and opposite to the front surface; the cassette further comprising a body defined by the aforementioned four elements, the body defining an internal bay portion with slots constructed by alignment grooves between adjacent dividers on the inner surface of the first side wall and the second side wall and support slabs displaced across two corresponding alignment grooves, wherein each slot can receive one wafer. The support slab extended between the first and the second side walls is used for supporting the wafer inside the semiconductor wafer cassette. Moreover, the body also includes two parallel legs for supporting the cassette and a handle for handling the cassette.
By the construction described above, the semiconductor wafer cassette of the present invention can completely support the wafer inside and has broadened slots. The semiconductor wafer cassette of the present invention not only reduces the drooping phenomenon of wafers placed in the cassette, but also provides wafers a bigger space with broadened slots and thus prevent wafers from damage during loading onto or unloading from processing machines.